Some further feedback on seeing your map in action:
1) Some of the civs aren't meant to play on regular terms. For instance, you placed Sibir, but it can't build settlers and researches at a reduced rate, so it just sits there with its one city. Generally speaking, I'd advise you to lose some civs and add some others. Lose: Sibir (not intended to compete on common terms with others), Venice (strange to have around as a separate civ, only serves to limit Rome's progress; makes more sense in a medieval setting), if you only want to have civs that can expand Netherlands and Portugal (though they work quite well as one-city civs), Mongols (they really should be much further to the East; I would probably just cut off more of Siberia with mountains, but I can see how having Mongols in makes for more fun).
2) Conversely, seeing how many free slots you still have, I'd say you're not bold enough adding other civs. For instance, our leader-specific name lists and lots of additional flags used in scenarios work rather well with creating several different civs out of one. We also have enough flags from other scenarios for such civs to use them. Examples I'd suggest considering (maybe not all at once, but some are definitely worth it): Scotland (another instance of Celtic civ, should use one of the Scottish leaders, Dravidian color as they're not on the map, and msc_flag_scotland.dds), Denmark (another instance of Scandinavian civ, should use Christian IV, Japan's color and fire and sword_flag_denmark.dds), maybe separate Viking civ in Norway (using Ragnar and msc_flag_viking.dds), Cilicia (Armenia, with Thoros as leader, Zulu (?) color and msc_flag_cilicia.dds as flag), Seljuks (Turks with Alp Arslan as leader, American color (generally since you have a lot of unused civs, scavenge their colors creatively) and msc_flag_seljuk.dds as flag), Greece proper (with Pericles, and Alexander becoming Macedon instead, seeing how Athens and Sparta are barbarian anyway right now), splitting Transoxiana into Timurids (led by Timur or Ulugh Beg) and Parthians led by Mithridates or Afghans led by Durrani (if you want to use Demetrius, Bactria is also a possibility, but it should start in a different place from now), maybe even separate Germany into Germany proper (led by someone else, like Otto) and Prussia (led by Frederick and using fire and sword_flag_brandenburg.dds, only a bit anarchonistic) or even create a separate starting Gaul faction for continental Celts with Vercingetorix (with Ireland getting celtic_ireland.dds and actually becoming Ireland), as well as splitting Berbers into Moroccans (where your current Berbers start) and Numidians (to the south of Carthage). I can even create some custom flags specifically for the ones you need (such as Macedonians) if you request them.
3) Some of the better developed unplayable civs could definitely find a home in this map, just like Finland did. Mughals (starting in Afghanistan or somewhat to the south), Austrians and Israel (though this last one is like Netherlands and Portugal in the sense of being a one-city civ) come to mind.
4) Since naturally some of the New World resources are absent from the map, one could simulate New World colonies and reward the first oceangoing civs by placing an American coast laden with resources across the Atlantic.
5) Placing barbarian cities on isolated islands is not recommended as this is what it leads to:
https://imgur.com/a/LMqTW. Lots of pointless units, negative performance impact. I'd suggest pre-placing stronger barbarian units there instead (bear in mind that pre-placed units shouldn't necessarily match their civ, so Crete can have some barbarian Greeks roaming it, for instance).
6) To my mind, you don't really need so many barbarian cities. You should probably use them to funnel civs into expanding in historical directions, but you probably don't need so many, especially in more densely-populated areas of the map, such as Western Europe. But of course, this is again up to you. I wouldn't go crazy on barbarian forts, as suggested above, though - they are there in the world map scenarios to prevent early overexpansion (like Incas conquering all of South America), but your map doesn't have much of a problem with that, as it's pretty evenly populated.
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